|Title||Single-crystal and polycrystalline diamond erosion studies in Pilot-PSI|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||D. Kogut, D. Aussems, N. Ning, K. Bystrov, A. Gicquel, J. Achard, O. Brinza, Y. Addab, C. Martin, C. Pardanaud, S. Khrapak, G. Cartry|
|Journal||Journal of Nuclear Materials|
Diamond is a promising candidate for enhancing the negative-ion surface production in the ion sources for neutral injection in fusion reactors; hence evaluation of its reactivity towards hydrogen plasma is of high importance. Single crystal and polycrystalline diamond samples were exposed in Pilot-PSI with the D+ flux of (4‒7) 1024 m−2s−1 and the impact energy of 7–9 eV per deuteron at different surface temperatures; under such conditions physical sputtering is negligible, however chemical sputtering is important. Net chemical sputtering yield Y = 9.7 10−3 at/ion at 800 °C was precisely measured ex-situ using a protective platinum mask (5 × 10 × 2 μm) deposited beforehand on a single crystal followed by the post-mortem analysis using Transmission Electron Microscopy (TEM). The structural properties of the exposed diamond surface were analyzed by Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). Gross chemical sputtering yields were determined in-situ by means of optical emission spectroscopy of the molecular CH A-X band for several surface temperatures. A bell-shaped dependence of the erosion yield versus temperature between 400 °C and 1200 °C was observed, with a maximum yield of ∼1.5 10−2 at/ion attained at 900 °C. The yields obtained for diamond are relatively high (0.5–1.5) 10−2 at/ion, comparable with those of graphite. XPS analysis shows amorphization of diamond surface within 1 nm depth, in a good agreement with molecular dynamics (MD) simulation. MD was also applied to study the hydrogen impact energy threshold for erosion of  diamond surface at different temperatures.
|Alternate Title||J. Nucl. Mater.|
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